This invention relates to vehicle cooling unit or systems, such as radiators, air coolers, and condensers, and more particularly, to transmissions for driving a radial fan in a vehicle cooling unit including a plurality of heat exchangers arranged to surround the radial fan to receive a radial air flow therefrom.
Vehicle cooling systems or units are know wherein a plurality of heat exchangers surround a radial fan in a box-like arrangement to receive a radial air flow therefrom.
One example of such a system is shown in unpublished application DE 199 50 753.8, which discloses a box-like radiator having a recessed rear wall in which a drive shaft of a radial fan is mounted and is equipped with a connection flange. The fan drive itself is characterized as being primarily situated in the space made available by the recessed rear wall.
A fan drive is shown in DE 41 17 336 A1 that can compensate for the relative movements between the engine and cooling unit. This is achieved by a motion compensation device arranged between the engine and fan and which is designed in a preferred example as an expansion bellows. The expansion bellows might have some advantages relative to known elastic shafts, but has thus far not gained acceptance, presumably because its suitability in long-term operation is restricted, since such an expansion bellows is subject to enormous stresses, which the employed materials may not withstand.
Fans in vehicles are often driven by means of drive belts, such as V-belts, which are arranged between a pulley on the crankshaft of the engine and a pulley on the shaft of the fan. To equalize the above mentioned relative movements and to counteract expansion of the V-belt, the V-belt additionally runs over a moving idler pulley. The moving idler pulley and the driving pulley are conventionally fastened to the engine housing. The engine also drives other auxiliary machines, like water pumps, hydraulic pumps, compressors and generators with the drive belt, so that, in many cases, a design restriction is produced, which hampers accessibility in the case of inspection and maintenance activities.
At the VTMS Conference in May 1999, three principles for arrangement and connection of the engine on the drive side to the fan of the radiator were presented. The first principle, attaches the radiator on the frame of the vehicle and mounts the fan on the radiator. This principle is shown in the previously mentioned DE 41 17 336 A1. This principle also is shown in WO 98/45600, which discloses a box-like cooling unit with a belt drive for the fan. In the second principle, the radiator and fan are mounted directly on the engine, whereas, in the third principle, the radiator is fastened to the frame and the fan is mounted on the crankshaft of the engine.
While many of the known cooling units may perform satisfactorily for their intended purpose, there is always room for improvement. For example, improvements may be made in terms of compactness, reliability of long-term operation, and ease of assembly.
According to one form of the invention, a transmission is provided for driving a radial fan about a fan axis in a vehicle cooling unit including a plurality of heat exchangers arranged to surround the radial fan to receive a radial air flow therefrom. The radial fan receives an axial air flow from a front end of the cooling unit. At least one of the heat exchangers has a rearmost edge that defines a back end plane transverse to the fan axis, with none of the other heat exchangers having a rearmost edge that extends rearward beyond the back end plane. The transmission includes a driven pulley mounted to the cooling unit for rotation about the fan axis and connected to the radial fan to transmit a drive torque thereto, a driving pulley having an axis of rotation substantially parallel to the fan axis and spaced radially from the fan axis, at least one drive belt extending from the driving pulley to the driven pulley to transmit drive torque thereto, a tensioning lever mounted to pivot about a pivot axis that is substantially parallel to the fan axis and spaced radially from the fan axis, and an idler pulley mounted on the tensioning lever for rotation about an axis that is substantially parallel to the fan axis and spaced from the fan axis, the pivot axis, and the axis of rotation of the driving pulley. The idler pulley is engageable with the drive belt.
In a preferred embodiment, the driving pulley, the driven pulley, and the idler pulley do not extend rearward beyond the back end plane.
In one form, an operating cylinder is engaged with the tensioning lever to selectively urge the tensioning lever to pivot about the pivot axis.
The invention is described below in practical examples, from which additional features and advantages of the invention follow.